The Argentavis is amazing for resource runs. The weight of Stone, Metal, Crystal, and Obsidian is halved. Also it works as a mobile smithy, meaning you can repair your metal tools on the go. They also have much higher Carry Weight than a Pteranadon and most of the time more Stamina and Melee Damage, so they can hold their own pretty well. They also have a crazy Health Regen buff when consuming corpses. Can also use it to transport bigger dinos. Their pretty slow though compared to most other flyers.